318 COSMOS. 



also with reference to its influence on the feelings and mental 

 condition of men. 



If the surface of the Earth consisted of one and the same 

 homogeneous fluid mass, or of strata of rock having the same 

 color, density, smoothness, and power of absorbing heat from 

 the solar ra3^s, and of radiating it in a similar manner through 

 the atmosphere, the isothermal, isotheral, and isochimenal 

 lines would all be parallel to the equator. In this hypothet- 

 ical condition of the Earth's surface, the power of absorbing 

 and emitting light and heat would every where be the same 

 under the same latitudes. The mathematical consideration 

 of climate, which does not exclude the supposition of the ex- 

 istence of currents of heat in the interior, or in the external 

 crust of the earth, nor of the propagation of heat by atmos- 

 pheric currents, proceeds from this mean, and, as it were, 

 primitive condition. Whatever alters the capacity for ab- 

 sorption and radiation, at places lying under the same parallel 

 of latitude, gives rise to inflections in the isothermal lines. 

 The nature of these inflections, the angles at which the iso- 

 thermal, isotheral, or isochimenal lines intersect the parallels 

 of latitude, their convexity or concavity with respect to the 

 pole of the same hemisphere, are dependent on causes which 

 more or less modify the temperature under difTerent degrees 

 of longitude. 



The progress of Climatology has been remarkably favored 

 by the extension of European civilization to two opposite 

 coasts, by its transmission from our western shores to a conti- 

 nent which is bounded on the east by the Atlantic Ocean. 

 When, after the ephemeral colonization from Iceland and 

 Greenland, the British laid the foundation of the first perma- 

 nent settlements on the shores of the United States of Amer- 

 ica, the emigrants (whose numbers were rapidly increased in 

 consequence either of religious persecution, fanaticism, or love 

 of freedom, and who soon spread over the vast extent of ter- 

 ritory lying between the Carolinas, Virginia, and the St. Law- 

 rence) were astonished to find themselves exposed to an intens- 

 ity of winter cold far exceeding that which prevailed in Ita- 

 ly, France, and Scotland, situated in corresponding parallels 

 of latitude. But, however much a consideration of these cli- 

 matic relations may have awakened attention, it was not at- 

 tended by any practical results until it could be based on the 

 numerical data of mean annual temperature. If, between 

 58^^ and 30*^ north latitude, we compare Nain, on the coast 

 of Labrador, with Gottenburg ; Hahfax with Bordeaux ; New 



